Internet Draft: IMAP UNSELECT command A. Melnikov
Document: draft-melnikov-imap-unselect-01.txt MessagingDirect
Expires: November 2003 May 2003
Intended category: Standards Track
IMAP UNSELECT command
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Please see the Full Copyright section near the end of this document
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Abstract
Certain types of IMAP clients need to release resources associated
with the selected mailbox without selecting a different mailbox.
While [IMAP4] provides this functionality (via a SELECT command with
an invalid argument or reselecting the same mailbox with EXAMINE
command), a more clean solution is desirable.
[IMAP4] defines the CLOSE command that closes the selected mailbox as
well as permanently removes all messages with the \Deleted flag set.
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However [IMAP4] lacks a command that simply closes the mailbox
without expunging it. This document defines the UNSELECT command for
this purpose.
A server which supports this extension indicates this with a
capability name of "UNSELECT".
Table of Contents
1. Conventions Used in this Document............................ 2
2. UNSELECT command............................................. 3
3. Security Considerations...................................... 3
4. Formal Syntax................................................ 3
5. Acknowledgments.............................................. 4
6. Normative References......................................... 4
7. Author's Addresses........................................... 4
1. Conventions Used in this Document
"C:" and "S:" in examples show lines sent by the client and server
respectively.
The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
in this document when typed in uppercase are to be interpreted as
defined in "Key words for use in RFCs to Indicate Requirement Levels"
[KEYWORDS].
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2. UNSELECT Command
Arguments: none
Responses: no specific responses for this command
Result: OK - unselect completed, now in authenticated state
BAD - no mailbox selected, or argument supplied but
none permitted
The UNSELECT command frees server's resources associated with
the selected mailbox and returns the server to the authenticated
state. This command performs the same actions as CLOSE, except
that no messages are permanently removed from the currently
selected mailbox.
Example: C: A341 UNSELECT
S: A341 OK Unselect completed
3. Security Considerations
It is belived that this extension doesn't raise any additional security
concerns not already discussed in [IMAP4].
4. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) notation as specified in [RFC-822] as modified by [IMAP4].
Non-terminals referenced but not defined below are as defined by
[IMAP4].
Except as noted otherwise, all alphabetic characters are case-
insensitive. The use of upper or lower case characters to define
token strings is for editorial clarity only. Implementations MUST
accept these strings in a case-insensitive fashion.
command-select /= "UNSELECT"
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5. Acknowledgments
UNSELECT command was originally implemented by Tim Showalter in
Cyrus IMAP server.
Also, the author of the document would like to thank Vladimir
Butenko and Mark Crispin for reminding that UNSELECT has to be
documented. Also thanks to Simon Josefsson for pointing out that
there are multiple ways to implement UNSELECT.
6. Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[IMAP4] Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 2060, University of Washington, December 1996.
7. Author's Addresses
Alexey Melnikov
ACI Worldwide/MessagingDirect
Address: 59 Clarendon Road, Watford,
Hertfordshire, United Kingdom, WD17 1FQ
Phone: +44 1923 81 2877
Email: mel@messagingdirect.com
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Acknowledgement
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